More than a month after the 9/11 al Qaeda attack on the U.S. Consulate in Libya, which left the U.S. ambassador and three other Americans dead, we are still no closer to knowing who knew what and when, and who should be accountable.

President Obama, speaking after Hillary Clinton took responsibility for the State Department’s security lapse at the Benghazi Consulate, said quite clearly last night that the buck stops at the Oval Office. Yet by refusing to answer a question from an undecided voter during the presidential debate with Republican nominee Mitt Romney at Hofstra University, the president muddied the waters still further. The questioner wanted to know: Who was it who denied enhanced security, and why?

Obama did say that “as soon as we found out that the Benghazi Consulate was being overrun, I was on the phone with my national security team.” That’s interesting, because Vice President Biden had suggested in the vice presidential debate last week that the White House was not micromanaging the response on the ground, and “we weren’t told they wanted more security there.”

Apparently contradicting Biden, Obama went on to say that he gave his security team three instructions — to beef up security and procedures at U.S. diplomatic missions, not just in Libya but around the region, to investigate exactly what happened, “regardless of where the facts lead us” to ensure that those responsible are held accountable and that it doesn’t happen again, and finally to track down and punish the perpetrators of the attack.

Obama had an opportunity last night to clarify what he knew about what happened. Biden was back on TV this morning defending the president and accusing the Romney campaign of continuing to politicize the tragedy. Obama himself reacted with barely concealed anger after Romney accused him of attending a fundraiser in Las Vegas the next day, reviving memories of George W. Bush going to a fundraiser on the West Coast after Hurricane Katrina devastated New Orleans. Obama and Romney then bickered over whether the president had described the attack, initially believed to be a spontaneous protest, as an “act of terror” by al Qaeda, the day after it occurred.

In a way, both the president and his Republican challenger blew it. Romney started to flail after Obama’s outburst, in which he said it was “offensive” that anyone on his team would play politics or seek to mislead on such an important national-security issue. But Obama has left the American public with still more questions over what happened in Benghazi on 9/11 and who is to blame.